1. What is the Cable Size Calculation?

The cable size calculation determines the appropriate cross-sectional area of electrical cable needed for a 15kW motor, considering current, cable length, resistivity, and allowed voltage drop.

2. How Does the Calculator Work?

The calculator uses two main formulas:

Where:

• \( A \) — Cable cross-section area (mm²)
• \( I \) — Current (A)
• \( L \) — Cable length (m)
• \( \rho \) — Resistivity (Ω·m)
• \( Vd \) — Allowed voltage drop (V)
• \( V \) — Voltage (V)
• \( PF \) — Power factor
• \( \eta \) — Motor efficiency

Explanation: The first formula calculates the required cable size based on current and voltage drop, while the second calculates the current drawn by the motor.

3. Importance of Proper Cable Sizing

Details: Correct cable sizing prevents overheating, ensures proper voltage at the motor terminals, and maintains system efficiency and safety.

4. Using the Calculator

Tips: Enter the motor voltage (typically 400V for 3-phase), power factor (usually 0.8-0.9), motor efficiency (typically 0.85-0.95), cable length, resistivity (0.0000000172 Ω·m for copper), and allowed voltage drop (typically 3-5% of supply voltage).

5. Frequently Asked Questions (FAQ)

Q1: Why is voltage drop important?
A: Excessive voltage drop can cause motor starting problems, overheating, and reduced performance.

Q2: What's a typical allowed voltage drop?
A: Generally 3-5% of supply voltage (12-20V for 400V systems).

Q3: How does cable length affect size?
A: Longer cables require larger cross-sections to maintain the same voltage drop.

Q4: What resistivity value should I use?
A: 0.0000000172 Ω·m for copper, 0.0000000282 Ω·m for aluminum.

Q5: Should I round up the calculated size?
A: Yes, always select the next standard cable size above the calculated value.